Knowledge of ganglion cell architecture and connections is prerequisite to understanding visual information processing in the retina and the relation between peripheral and central sensory organizaton. Four anatomical parameters of retinal ganglion cells are known to have functional significance: 1) the spatial distribution of ganglion cells as a whole and the differential distribution of each ganglion cell class; 2) ganglion cell morphology, including size classes and dendritic architecture; 3) the types and distribution of synaptic contacts onto ganglion cells in the inner plexiform layer; and 4) the pattern of ganglion cell central projections. In experiments already completed or under way, I am describing the spatial distribution, size classes and central projections of retinal ganglion cells in Pseudemys scripta elegans. The proposed research will extend this analysis of ganglion cell functional morphology. I will 1) determine dendritic morphology of ganglion cell classes as visualized in Golgi preparation of both wholemounted and sectioned retinas; and 2) characterize the first order afferent contacts of each ganglion cell class by examining the type and distribution of synapses onto identified, Golgi impregnated ganglion cells under the electronmicroscope. This research, combined with work in progress, will contribute to our understanding of visual processes in two ways. The proposed research will provide the first comprehensive and systematic attempt to relate the organization of the retina to that of the central pathways in any non-mammalian vertebrate. Second, the proposed rsearch will contribute toward our understanding of the turtle retina which has become an important preparation in retinal neuroscience.